Question

The earth's magnetic induction at a certain point is $7 \times 10^{-5} Wbm ^{-2}$. This is to be annulled by the magnetic induction at the centre of a circular conducting loop of radius $15\, cm$. The required current in the loop is

• A. 0.56 A
• B. 5.6 A
• C. 0.28 A
• D. 2.8 A

Answer 1

Answer: (B)

From, $B=\frac{\mu_{0} i}{2 r}$,
$7 \times 10^{-5}=\frac{4 \pi \times 10^{-7} \times i}{2 \times 5 \times 10^{-2}}$
$\therefore i=\frac{7 \times 10^{-5}}{4 \pi \times 10^{-6}}=5.6\, A$